This application is related to commonly-assigned U.S. patent application Ser. No. 11/928,038, filed on 30 Oct. 2007.
The present invention relates to the exhaust gas emitted from a turbomachine, and more particularly to a system for reducing the sulfur oxides within the exhaust gas before recirculating the exhaust gas back into the turbomachine.
There is a growing concern over the long-term effects of Nitrogen Oxides (hereinafter NOx) and Carbon Dioxide (hereinafter “CO2”) and Sulfur Oxides (SOx) emissions on the environment. The allowable levels of emissions that may be emitted by a turbomachine, such as a gas turbine are heavily regulated. Operators of turbomachines desire methods of reducing the levels of NOx, CO2, and SOx emitted.
Significant amounts of condensable vapors exist in the exhaust gas stream. These vapors usually contain a variety of constituents such as water, acids, aldehydes, hydrocarbons, sulfur oxides, and chlorine compounds. Left untreated, these constituents will accelerate corrosion and fouling of the internal components if allowed to enter the gas turbine.
Exhaust gas recirculation (EGR) generally involves recirculating a portion of the emitted exhaust through an inlet portion of the turbomachine where it is mixed with the incoming airflow prior to combustion. This process facilitates the removal and sequestration of concentrated CO2, and also reduces the NOx and SOx emission levels.
There are a few problems with the currently known EGR systems. Impurities and moisture within the exhaust gas prevent utilizing a simple re-circulating loop to reduce the generation of emissions, such as SOx emissions. Turbine fouling, corrosion, and accelerated wear of internal turbomachine components would result from introducing the exhaust gas directly to the turbomachine inlet portion. As a result, the diverted exhaust gas should be treated prior to blending with the inlet air.
For the foregoing reasons, there is a need for a system for reducing the level of SOx emissions within the recirculated exhaust gas stream. The system should minimize impact of the harmful constituents within the exhaust gas stream on turbomachine components.